Lead-free plain bearing and method for its manufacture

Abstract

A lead-free plain bearing is formed by dispersing an alloy powder formed from 7-13 mass percent of Sn, 0.1-5 mass percent of Ag, and Cu on a backing, such as a steel plate, and sintering. The alloy powder may further include one or more of 0.05-0.5 mass percent of molybdenum disulfide powder and 0.1-2 mass percent of graphite powder. The bearing surface may be rough finished by machining to a roughness of 0.3-1 mum Ra and then fine finished by polishing to a roughness of at most 0.1 muRa.

What is claimed is:  
     
       1. A lead-free swash plate for a swash plate pump comprising a backing and a powder consisting essentially of 7-13 mass percent of Sn, 0.1-5 mass percent of Ag, and a remainder of Cu sintered to the backing to form a bearing surface on the backing. 
     
     
       2. A swash plate as claimed in  claim 1  wherein the bearing surface has a roughness of at most 0.1 μm Ra. 
     
     
       3. A swash plate as claimed in  claim 1  wherein the backing comprises a steel plate. 
     
     
       4. A swash plate as claimed in  claim 1  wherein the backing comprises a steel disk. 
     
     
       5. A swash plate as claimed in  claim 1  having a central hole in the backing for receiving a shaft of a swash plate pump. 
     
     
       6. A swash plate as claimed in  claim 5  having a plurality of holes surrounding the central hole for securing the swash plate to a shaft of a swash plate pump. 
     
     
       7. A method of manufacturing the swash plate of  claim 1  comprising: 
       dispersing the powder of  claim 1  on a backing; and  
       sintering the powder to the backing in a hydrogen atmosphere at 840-880° C. to form a bearing surface on the backing.  
     
     
       8. A method as claimed in  claim 7  including: 
       refining the bearing surface by pressing with a load of 300-500 MPa; and  
       annealing the bearing surface in a hydrogen atmosphere at 840-880° C. after refining.  
     
     
       9. A method as claimed in  claim 8  further including: 
       rough finishing the bearing surface after annealing to a surface roughness of 0.3-1 μm Ra; and  
       polishing the bearing surface after rough finishing to a roughness of at most 0.1 μm Ra.  
     
     
       10. A method of operating a swash plate pump comprising rotating the swash plate of  claim 1  with a rotational shaft of the pump to reciprocate a piston of the pump. 
     
     
       11. A lead-free swash plate for a swash plate pump comprising a backing and a powder consisting essentially of 7-13 mass percent of Sn, 0.1-5 mass percent of Ag, at least one of 0.05-0.5 mass percent of molybdenum disulfide and 0.1-2 mass percent of graphite powder, and a remainder of Cu sintered to the backing to form a bearing surface on the backing. 
     
     
       12. A swash plate as claimed in  claim 11  wherein the bearing surface has a roughness of at most 0.1 μm Ra. 
     
     
       13. A swash plate as claimed in  claim 11  wherein the backing comprises a steel plate. 
     
     
       14. A swash plate as claimed in  claim 11  wherein the backing comprises a steel disk. 
     
     
       15. A method of manufacturing the swash plate of  claim 11  comprising: 
       dispersing the powder of  claim 5  on a backing; and  
       sintering the powder to the backing in a hydrogen atmosphere at 840-880° C. to form a bearing surface on the backing.  
     
     
       16. A method as claimed in  claim 15  including: 
       refining the bearing surface by pressing with a load of 300-500 MPa; and  
       annealing the bearing surface in a hydrogen atmosphere at 840-880° C. after refining.  
     
     
       17. A method as claimed in  claim 16  further including: 
       rough finishing the bearing surface after annealing to a surface roughness of 0.3-1 μm Ra; and  
       polishing the bearing surface after rough finishing to a roughness of at most 0.1 μm Ra.  
     
     
       18. A swash plate as claimed in  claim 11  having a central hole in the backing for receiving a shaft of a swash plate pump. 
     
     
       19. A swash plate as claimed in  claim 18  having a plurality of holes surrounding the central hole for securing the swash plate to a shaft of a swash plate pump. 
     
     
       20. A method of operating a swash plate pump comprising rotating the swash plate of  claim 11  with a rotational shaft of the pump to reciprocate a piston of the pump.